leetcode-52. N-Queens II

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leetcode-52. N-Queens II

题目：
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Follow up for N-Queens problem.

Now, instead outputting board configurations, return the total number of distinct solutions.

跟上一题一样，比上一题简单。51-N-Queens I

public class Solution {private int ret = 0;public int totalNQueens(int n) {boolean [][] mat = new boolean[n][n];helper(mat,0);return ret;}private void helper( boolean[][] mat,int len){if(len==mat.length){ret++;return ;}for(int i=0;i<mat.length;i++){if(verify(mat,len,i)){mat[len][i] = true;helper(mat,len+1);mat[len][i] = false;}}}private boolean verify(boolean[][] mat, int ni , int nj){for(int i = 0 ; i<ni ; i++){if(mat[i][nj]) return false;if(ni-i-1>=0 && nj-i-1>=0 && mat[ni-i-1][nj-i-1]) return false;if(ni-i-1>=0 && nj+i+1<mat.length && mat[ni-i-1][nj+i+1]) return false;}return true;}
}

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